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Pulse pressure and the risk of post-epidural fetal heart rate (FHR) abnormalities: a randomized controlled trial
Abstract Number: GM-03
Abstract Type: Original Research
FHR abnormalities and maternal hypotension occur commonly after the initiation of neuraxial analgesia. Narrow pulse pressure (PP), a marker of low central volume status, may predict these post-epidural complications. We tested the hypothesis that increasing the IV fluid bolus in women with narrow PP would reduce post-epidural FHR abnormalities and hypotension.
We performed a single-center randomized controlled trial. Eligible participants were normotensive with singleton gestations ≥ 35 weeks and a narrow PP (<45 mmHg) on admission. Enrolled patients remained eligible for randomization at epidural request if they were ≤ 6 hours from admission and FHR remained category 1. Patients were randomized to 500mL (institutional standard) or 1500mL of IV fluid prior to epidural placement. A reference arm with admission PP>50 mmHg matched for BMI was also evaluated. The primary outcome was the incidence of new-onset category 2 or 3 FHR patterns in the 60 minutes following epidural placement. Primary outcome events were determined by a member of the research team blinded to study group. Secondary outcomes included hypotension, interventions (to correct FHR abnormalities or hypotension) or adverse events. We estimated needing 138 women per group to show a 50% reduction in the primary outcome from a baseline of 27% with 80% power and 2-tailed alpha of 0.05.
276 women with narrow PP were randomized to 500 mL (n=139) or 1500 mL (n=137). 138 women enrolled in the reference arm. Demographic, obstetric and labor management characteristics were similar among groups. A significant reduction in the incidence of new-onset FHR abnormalities was observed with 1500mL IV fluid (51.8% vs 38.0%, p=0.02). Hypotension and post-epidural interventions were also reduced in the 1500mL group. However, the risk of new-onset FHR abnormalities and hypotension remained significantly lower in the reference group (Table).
Increasing IV fluid preload in women with a narrow PP decreases the risk of post-epidural FHR abnormalities (NNT=7). Additionally, increasing IV fluid preload decreases the risk of post-epidural hypotension and interventions. While the risk of post-epidural complications was reduced with increased IV fluid administration, they were only attenuated when compared to a reference group with normal PP. Admission PP reflects maternal central volume status and may direct the individualization of intrapartum fluid management.